


let's try something new

by Ajpuppy



Category: Undertale
Genre: Cunnilingus, Foursome, Hand Job, M/M, Teasing, Voyeurism, kinda selfcest?, safe words
Language: English
Status: Completed
Published: 2018-01-13
Updated: 2018-01-13
Packaged: 2019-03-04 02:41:08
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,624
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/13354782
Author URL: https://archiveofourown.org/users/Ajpuppy/pseuds/Ajpuppy
Summary: The underswap brothers decide to play with the Swapfell brothers.





	let's try something new

underswap sans = Blue 

Underswap Papyrus = Stretch 

Swapfell sans = Black 

Swapfell Papyrus = Slim 

Let's try something new 

"I....I don't know about this." 

"Hm? You know your safe words don't you?" 

"…." 

"Safe words." 

"G-green, yellow, red." 

He leans in with a chuckle and pats the other's head. "Good boy, see? You can tell us slow or even to stop. Anytime at all." 

 

Blue squirmed a bit, blushing bright blue. How he'd actually agreed to playing these games with them he'd never know. Now he was completely unclothed, wrists tied behind his back, and stuck under the gaze of Black, slim, ….and his brother. It was incredibly unnerving, enough so that black stood in front of him now trying to hush him and 'cease that damn squirming'. 

Said skeleton knelt down with a pleased smirk and traced his finger under his look alike's chin. "Listen now." Black crooned lightly. "I'm the ring master here, the leader of these games. I make the rules, the punishments....and the rewards~" As he spoke he ran his fingers teasingly over the other monster's ribs, making Blue shudder with pleasure. "So relax, let me play with you as I wish. You'll find you won't regret your decision." Black purred, well aware of the taller sweater clad male eyeing Blue both hungry and possessive yet unable to do anything. 

Blue gave a quiet moan, not sure it was possible to blush any harder at Black's lewd and tempting words. His eyes darted away from the other in front of him, but the attempt to break eye contact only left him staring straight into the lusting hungry eyes of slim who sat in the dim corner. His eyes seemed to glow with barely contained desire, the taller skeleton only held back from ravaging him by the word of his lord. Squeaking, Sans once again averted his eyes, this time meeting...his brother's. He swallowed hard, unable to stop staring. 

Stretch had been commanded to stay still, prohibited to move or touch Blue. No, he was only allowed to be a spectator to Black's games at the moment. The darker version of his cute little brother hadn't even started, and yet Stretch wanted nothing more than to ravage his brother just from seeing him vulnerable and tempted. Upon seeing the other's shy and worried look he quickly realized that Blue was looking to him to make sure this was okay. Trying to give him a soothing look of approval past his own need he nodded. This had been a decision that had to be made by both of them after all. It was no secret that Blue and Stretch had been an item, but that didn't mean that the two wouldn't be interested in trying new things and that was when Black came to them with a proposition. 

Receiving the nod of approval, Blue's shoulders relaxed the slightest bit. Black leaned down with a low pleased rumble, "Safeword?" 

"….Green." 

Black's eyes glowed with anticipation, with a delighted hum he leaned in close to Blue until their breaths mingled. "Gooood boy, now let's give you a taste of what's to come hm?" Pressing their teeth together black kissed his softer look alike. He tasted...sweet. The other monster's mouth was submissive as he licked his tongue over Blue's teeth to which the other curiously let him inside. 

Blue gave a soft mewl, hands moving against his bindings a bit as he felt the need to touch Black but was denied. The other's hands had moved to tease his collar bones and the vertebrae of his neck. Such places were sensitive and by the sly look on Black's face, he knew that. The room was silent except for the small skeletons pleased murmurs, and the soft thrum of multiple sources of aroused magic. "B-Black." He mumbled, breath hitching as the other had broken their kiss to move his mouth lower. 

"Mm?" The darker male was focused on kissing and nipping his doppelganger's vertebrae and under his jaw, not mentioning at all that this was something slim did to him that he just so happened to really enjoy too. He slightly glanced at the other two male's in the room to make sure he still had their attention. Indeed he had, Slim was watching them intently like a stud ready to breed heated bitches. Despite his heavy panting and clear glowing arousal through his pants, he obediently stayed still and waited for his master's commands. Switching his attention to Stretch, it seemed the tall male must've only had eyes for Blue. Stretch didn't seem to know what to do with his hands, unallowed to touch himself he was now fidgeting as he stared at his brother and clearly ached to touch him. How cute. 

Black smirked, deciding to tease the two Papyrus' further. Reaching up he touched his hand gently at the beginning of Blue's sternum, then slowly slid down. He touched to the ends of the bone, listening to his counterpart's hitching breaths and watching his face carefully. As Blue shuddered into the touch, Black continued and teased a finger around the other's spine, slow enough to make the other wiggle his hips in anticipation. What a perfect little toy~ He took his time around the other's pelvis, touching over the arches, inside where the bones opened, around the joints, and even closer to Blue's beautifully summoned and already moist baby blue pussy. But he wouldn't touch there, not yet. The game can't end to quickly and he had plans to exact before the real show began. 

Blue whimpered and tried not to buck his hips with all this teasing. Black was so slooow! He clenched his fists as those fingers teased down his nude body, anywhere but where he really wanted them. He wanted to touch black and hold onto him as to keep himself grounded. "P-please." He mumbled. "G-green, I want- I need-" He couldn't finish the sentence, panting and trying his best to stay still yet failing. 

"Hush pet. Patience is a virtue, and you will get what I decide to give you and only then." 

Black's tone was patient with Blue, perhaps because he was unused to these activities with the Swapfell brothers. Blue gave a soft whimper, but nodded submissively and waited. The darker version seemed to watch him for a good moment, making him squirm nervously as Black had stopped touching him all together. What was the other thinking? He could only watched as the other turned away from him and eyed stretch. 

Black eyed the tall male with a smug expression and hummed. It seemed Blue was fully settled now into this little game, as were the other two. Perhaps phase two was necessary before things got old. Stretch was watching like a hawk, and slim was starting to get antsy. Stretch would have too remain patient for his prize. "Come here, Mutt." He commanded, calm and firm. Slim got up and walked briskly to his side with an eager "Yes, M'lord." 

Black watched Stretch for a moment, noticing that this had caused just the reaction he wanted and the now lone Papyrus looked even more wanting. “Alright dog.” The smaller male spoke, “why don't you be useful for once, and show little Blue what a tongue feels like?” 

Naïve, vanilla little Blue looked confused to this command. But Stretch who'd been pretty still thus far, tensed. Another Papyrus would be doing something quite lewd with his brother. A papyrus that wasn’t him. He’d….. considered doing things like that with Blue before sometime ago. But they'd both been usually eager to get to the good stuff and find their release with no time for waiting. 

Slim licked his lips, nodding and getting down on a knee between Blue's legs making the smaller skeleton fluster and look away. “That’s um…” he swallowed hard and shifted his hips a little away from slim, hoping he couldn’t smell the quite evident arousal. 

Slim gently grabbed and spread Blue's legs, but as he was about to get to work, Black spoke, 

“Don't let him finish, Mutt. Nothing satisfactory. We both know you can be insufferable with your teasing, don’t we?” 

Slim smirked and licked a long thick bright orange tongue over his fangs and practically purred, “yes, M'lord.” He dipped down slowly and traced his tongue over the outer lips of Blue's pussy, reveling in the shocked and pleasured squeak the more innocent version of his Lord made. He couldnt lie and say that he hadn't been pretty excited when his brother told him who they'd be playing with. He'd wanted to have Blue underneath him for sometime. The Swapfell brothers were much like the underswap brothers in the fact that romantically they were quite exclusive, but with permission playing with others from time to time was allowed. Not that it happened too much since Slim's only interest really was his Lord. But Blue…. Blue was innocent, Blue was loud, Blue was….expressive. He was his Lord with a more honest face, the same voice…and more open screams of pleasure~ 

Slim had never thought he’d one day get a chance to do this due to Stretches protective nature over the smaller male, but here they were. He dipped his tongue in, just slightly spreading the labia apart before taking in the smaller monster's taste. Blue was already starting to squirm and it was quite pleasing. 

Blue whined softly, his face glowing bright Blue as he'd never done this before. Stretch was-was licking him down there! On one hand he felt absolutely mortified, on the other- "A-ah!" His hips wiggled as he wanted the other Papyrus to go deeper with that delicious tongue. This was incredibly lewd, and the soft wet noises produced from their activity was both embarrassing and arousing. Suddenly Stretch had done something different. Instead of a small teasing lick, the other had given a long slow caress starting from the bottom and ending with him flicking his tongue across Blue's clit. The smaller monster jerked and let out a sharp pleased cry. He tried to close his legs around Slim's head, but the other held his femurs spread apart. It seemed slim wasn’t playing too much anymore because he started to pleasure the other at a steady pace, licking anywhere BUT that amazing little nub. Blue whined desperately as the other even teased a finger at the beginning of his entrance, rubbing the hard ridge but not dipping inside. 

Stretch was still seated, watching intently as his sibling squirmed and mewled. He'd been quiet thus far, still even, but it didn’t mean he wasn't affected by this. No, Blue's pleased cries and squirming were actually driving him nuts. His cock was straining hard against his pants zipper, it wasn't pleasant. His bones felt heated in his hoodie and he wanted nothing more than to join the other's in ravaging his lover. But if he disobeyed Black's command to stay it would only get worse from there. It didn't help that the darker version of his brother seemed to be watching him closely with interest, that like a cat watching it's prey. ...The other was pleased with his silent wanting wasn't he? Black seemed to watch him, not interested in the sexual acts going on just behind him. What was he planning? He rose a brow as the other started to walk towards him. 

The darker Sans knelt down with a smirk. "You're enjoying yourself quite a bit aren't you?~ Don't answer. The glow of your pants tells me all that I need to know." He chuckles, teasingly sliding a finger over the other's clothed cock and making Stretch's body jerk. "How about we make this a little more interactive hm?" He reached for Stretch's zipper and ever so slowly pulled It down. As it reached the end of it's track the Papyrus' cock sprung out, completely hard and pre cum beading at the tip. Black licked his lips. "Hmm, already so eager. Will you be as responsive as your brother I wonder?" Slowly stroking his hand once from base to tip and watching Stretch give a huffy moan he chuckled. "Now stand for me." He watched as the other got up, a little wobbly from sitting the whole time and his current predicament. 

"What do you have in mind now, 'ring master'?" Stretch tried to hum coolly, but the waver in his voice gave away how aroused he really was. 

"Hush, you. You will wait and see." Black quipped, lightly flicking Stretch's cock as punishment for his cheekiness. He smirked as the other jolted and gave a hiss that didn't sound completely of pain. Perhaps he was like Black's Papyrus in the sense that he liked a little pain too? 

Stretch swallowed and watched Black, all too aware of the sweet noises and pleads his brother was making. The smaller male in front of him was teasing the base of his cock, slowly sliding a clawed phalange up the shaft and teasing his tip by dipping the tipped claw ever so slightly into his urethra. He found himself finding it much harder to save face when he was being touched directly. Grunting, he tried to keep his hips still from shaking. Fuck, he'd been forced to wait for anything at all so far and now he was being teased just like his brother. Did these two have endless patience, or just get their rocks off by making others wait? Stretch's hands twitched with the want to grab black and get on with the good stuff. But the other noticed it and Black's eyes shone dangerously with warning should he try. 

Blue's cries got louder and everyone's attention was brought back to him. "P-please I-ah!~ I need it now, please I can't take this anymore." He'd been being teased this whole time by slim, eaten out, licked and nibbled everywhere but where it was REALLY wanted. The small male could only try and buck his hips to gain more of the pleasure, but even then Slim's grip was strong and firm. With each caress of that sinful tongue Blue's muscles tightened and squeezed nothing, trying to pull a phantom cock deep inside himself where there was none. 

His begs seemed to be affecting slim quite heavily too. His jaw was becoming tired, his cock had leaked precum enough to where a dark patch was visible through the front of his pants. He panted heavily and his body shook with wavering control to follow his Lord's orders. Glancing over at Black, he licked his teeth clean from Blue's magic. 

Black hummed in thought, stroking Stretch with small pleasuring but hardly satisfying movements. He'd grown pretty wet himself at this point, and it was very clear everyone was eager to get to the main event. If they drew it out any longer anticipation could lead to frustration. He was pleased when Blue's mewls had Stretch's cock jumping hard in excitement in Black's hand. Perhaps it really was time to give them something more. Standing straight, he abandoned the other's member and began walking back over to the other two. "Come along, Stretch. I suppose you've all been good enough to receive a treat." He was amused when the other had to waddle after him. Mmm a good hard cock wasn't always the easiest to handle. Glancing back over at Blue, Blacks own Pussy clenched a bit. The other's flustered and pleading face was one to behold. The other version of himself squirmed in need. It made even Black want to take him hard and fast. But Black topping Blue would be left for another time. Sancest between the two doppelgangers could be another adventure planned in the future. 

"M-my lord?" 

Slim's shaky murmur broke Black out of his fantasy and he quickly nodded. "Mutt, cock out." Slim seemed pretty enthusiastic to follow that order. Unzipping his pants and bringing out his hard leaking member, both Papyrus' were now showing of how well endowed they were. Both Black and Blue found themselves staring hungrily for a moment before Black shook it off and began to fully undress save for his Bandana. Blue had requested the same be left on his person. Naturally Black felt his lover's lusting eyes on his nude form, but Stretch was also looking over his scarred bones curiously. The small dark skeleton blushed a little and tried to hide the bashful moment with standing tall and a firm ordering voice, " Now come here to the bed, Slim, free Blue's wrists." 

As Blue was freed he moved towards the bed in the middle of the room. Walking wasn't quite comfortable with the heated liquid running down his bones. Black climbed onto the large bed and motioned his counter part to do the same. The smaller more innocent male didn't seem sure what to do from here, but Black pulled the other close and began to kiss him deeply. Blue squeaked but was quick to engage in making out. For a few moments they passionately kissed, leaving the Papyrus' to only watch before Black lifted a hand and crooked his finger at them in a 'come here' motion. 

Slim was quick to get on the bed behind Black, while Stretch got behind Blue. As Black nodded his approval the two lined themselves up to slide inside their lovers. Black grunted in slight pain as Slim jerked his hips sharply and buried himself inside with a low pleased moan. He didn't bother to wait as he began to move in sharp jerky thrusts. Black bit his lip to hold in any noises but a muted pleasured expression could be seen. 

Stretch had been a little slower for Blue, sliding in and giving a grunt while Blue moaned brokenly as his wet hot pussy had been stretched. It had been about time that somebody was finally in him! Out of patience the two Papyrus' wasted no time in finding a matching rhythm. Black and Blue gripped at the sheets. Blue was much noisier than Black, but the smaller dark skeleton couldn't say he didn't enjoy the noises the other version of himself made. Quickly Black reconnected his lips with Blue's, moaning into the other's mouth and twining their tongues as the taller skeleton's plowed them from behind. The bed squeaked in protest to their combined weights, the sound of springs and bone on bone noises filling the rooms. 

Slim was biting down onto Black's shoulder, huffing loudly as he held tightly onto his lover's hips. He both loved and hated to be teased. Teasing felt good and he loved the attention of his lord, but at the same time his patience was shit. Combine having to wait with the honest moans of Blue had made it even harder to wait and made slim incredibly horny. His lover had been incredibly wet upon sliding deep inside. Despite Black's cool composure it seems that this game had excited him just as much. He was tight and squeezing around Slim like a vice, making the taller monster grunt and try to slam even harder inside. Seeing the two smaller monsters making out made him file the sight away in his head to recall at a later pleasurable time to himself. He wasn't sure how long he would last this time, not with how Black was subtly rocking back into his thrusts. 

Even Stretch was feeling a little less patient than normal after having to wait and hear his adorably sexy brother moan and watch him wiggle with need. With his fingers twined with Blue's, he thrusted deep into the other and buried his face into the vertebra of Blue's neck, mumbling passionate words of love and even dirty things of how he never knew his innocent baby brother could beg so cutely like a little whore. Such words made Blue mewl lewdly and buck his hips more. The squirming bodies on the bed became quicker and much more rough as the pleasure rose 

Black panted and arched, composed face breaking as he commanded his pet to move harder, to touch his clit. He became more demanding and even a bit higher pitched in voice as the pleasure took him. 

Blue was already incredibly close, having been teased so long and having his Papyrus whispering dirty things in his nonexistent ear. He rocked quickly back into the other's thrusts, moaning as Stretch went deep inside him. "T-touch me." He whimpered, and moaned loudly as the other did so. It was too much, and the pleasurable coil was tightening quickly. Blue was the first to cum, the coil snapped and the small skeleton's body went tense as he let out a loud whine of "Papyrus!" It didn't take long for the taller skeleton to cum either, unused to these games and waiting he quickly finished with a grunt as he unloaded heavy spurts inside his lover. 

This left the other two for them to watch. Black composure and care to stay that way was gone by now, he had made Slim let him turn around so they could kiss. Black hung onto Slim's shoulders, seated in his lap as his lover's cock thrusted sharply inside at a bed rocking pace. It was brutal and soft growls and cries were heard from the two as they finished with their own pleasure and laid back down in a panting heap. The room smelled heavily of sex and sweat and black, still cuddled in Slim's arms, looked over with a tired smirk. "How was that for shaking things up?" 

It seemed Blue had already fallen asleep, exhausted in Stretch's arms. The taller skeleton didn't look to far behind him but smirked. "We....we will have to do this again sometime."


End file.
